This disclosure is based upon French Application No. 99/05394, filed on Apr. 28, 1999 and International Application No. PCT/FR00/1149, filed Apr. 28, 2000, which was published on Nov. 9, 2000 in a language other than English, the contents of which are incorporated herein by reference.
The present invention relates to the manufacture of a portable electronic device, having at least one integrated circuit chip embedded in a support and electrically connected to interface elements constituted by a connection terminal block and/or an antenna.
These portable electronic devices constitute for example smart cards, with and/or without contacts, or electronic labels.
Smart cards with and/or without contacts are designed for carrying out various operations such as, for example, banking operations, telephone communications, various identification operations, or remote ticketing type operations.
Cards with contacts have metallizations exposed on the surface of the card, disposed at a precise place on the card body, defined by the usual standard ISO 7816. These metallizations are designed to come into contact with a read head of a reader with a view to electrical data transmission.
Contactless cards have an antenna making it possible to exchange information with the outside world by means of electromagnetic coupling between the card electronics and a receiver or reader. This coupling can be performed in read mode or in read/write mode, and the data transmission takes place by radiofrequency or ultrahigh frequency.
There are also hybrid cards or xe2x80x9ccombicardsxe2x80x9d which have both metallizations exposed on the surface of the card and an antenna embedded in the body of the card. This type of card can therefore exchange data with the outside world in either contact or contactless mode.
As implemented at present, the cards, with or without contacts, are portable items of small thickness and standardized dimensions. ISO standard 7810 corresponds to a standard format card, 85 mm long, 54 mm wide and 0.76 mm thick.
The majority of smart card manufacturing methods are based on assembly of the integrated circuit chip in a sub-assembly referred to as a micromodule which is inset, that is to say placed in a cavity made in the card body, using techniques known to persons skilled in the art.
A conventional method of manufacturing a micromodule with contacts is illustrated in FIG. 1. Such a method consists of gluing an integrated circuit chip 10 by disposing its active face with its contact pads 12 upward, and gluing its opposite face on a dielectric support sheet 15. The dielectric sheet 15 is itself disposed on a contact grid 18 such as a metal plate made of nickel-plated and gold-plated copper for example. Connection wells 16 are made in the dielectric sheet 15 in order to allow connecting wires 17 to connect the contact pads 12 of the chip 10 to the contact areas of the grid 18.
According to certain variants, it is possible to glue the chip 10, active face upward, directly on the contact grid 18, and then connect it by wiring 17.
In the case of a contactless micromodule, an antenna, deposited on the dielectric support by serigraphy or some other means, is connected to the metal grid.
In a variant embodiment, the chip can also be glued on a dielectric support and connected to defined connection areas on said support. The micromodule thus obtained can subsequently be connected by soldering or gluing to a wire antenna, etched or deposited by serigraphy.
A protection or encapsulation step next protects the chip 10 and the soldered connecting wires 17. Use is generally made of a technique referred to as xe2x80x9cglob topxe2x80x9d, which designates the coating of the chip from the top. This technique consists of using a drop of resin 20, epoxy-based for example, thermosetting or cross-linked by ultraviolet.
Generally, use is made of a three-dimensional thermal resin which requires a polymerization step under operating conditions onerous to implement. This is because time in an oven at over 90xc2x0 C. for a period of possibly as much as 24 hours is necessary, which necessitates an extended method time, suitable equipment and the intervention of an operator.
It is also possible to use resins polymerizable by exposure to ultraviolet. However, such resins are generally too flexible, which leads to electrical operation and stress problems when the chip is subjected to bending forces.
Resins polymerizable by ultraviolet are therefore rarely used directly as protection according to the conventional xe2x80x9cglob topxe2x80x9d technique.
Deposition of the resin 20 on the chip and the connecting wires can be carried out directly on the dielectric film for chips of small dimensions.
Nevertheless, in order to limit the risks of the resin running over the edges of the circuit, it is advantageous to delimit the surface of spreading of the drop of resin by a barrier so as to obtain a reproducible protective shape.
FIG. 2 illustrates deposition of a barrier 25 on the dielectric film 15. This barrier 25 can be made of polymer, such as epoxy, silicone or a polyester. It surrounds the chip 10 and can be deposited on the dielectric film 15 by serigraphy or by a distribution method.
This barrier 25 can also consist of a metal frame stamped and glued on the dielectric film 15 around the chip 10.
Depending on the particular case, this barrier 25 is deposited on the support 15 in a step of the manufacturing method, or it can be delivered directly by the supplier of the dielectric support 15.
The presence of a barrier 25 surrounding the chip 10 facilitates deposition of the protective resin 20 but does not necessarily make it possible to avoid the milling step, essential when too large a drop of resin has been deposited. This is because the drop of resin can hamper insetting of the micromodule by an overlarge excess thickness.
Milling makes it possible to optimize the height and shape of the protective resin.
However, milling constitutes a stressful operation for the connected chip.
Furthermore, this operation requires great precision in order not to damage the connection or the active face of the chip.
In addition, milling constitutes an additional step in the manufacturing method and has a non-negligible cost.
A micromodule 50, constituted by the chip 10 transferred on to the dielectric support strip 15 and connected to a communication interface 18, is next inset in the cavity of a previously decorated card body.
This insetting operation can be performed by deposition of a liquid glue in the cavity of the card body before transfer of the micromodule, or by deposition of a heat-activated adhesive film by hot rolling on the dielectric film 15 and by hot pressing by means of a press, the shape of which is adapted to that of the cavity of the card body.
These conventional methods of manufacturing micromodules nevertheless have many drawbacks.
On the one hand, the presence of a ring for confining the protective resin is often not sufficient to avoid milling. There results therefrom a covering of the chip which is not optimized and there is not full control over the geometry of the micromodule, in particular on the edges of the chip. Overflow of the resin can lead to the micromodule being scrapped.
It is important to have good control over the thickness of the micromodule, and therefore the height of the protective resin, in order to produce extra flat integrated circuit devices.
Furthermore, the fitting or purchase of a film with a barrier, whatever this is, and/or the milling of the resin have a non-negligible cost.
On the other hand, the use of a thermal resin, traditionally used in the conventional encapsulation technique, imposes too long a polymerization time for a continuous manufacturing method.
The aim of the present invention is to overcome the drawbacks of the prior art.
To that end, the present invention proposes a smart card manufacturing method making it possible to combine reliability of the finished product with simplicity and a reduction in the number of manufacturing steps.
In particular, the present invention proposes depositing protection for the micromodule using a method known by the name xe2x80x9cDAM and FILLxe2x80x9d which designates a method of protecting the integrated circuit chip in two steps.
First, a high-viscosity resin band, xe2x80x9cDAMxe2x80x9d, is deposited around the chip and its connecting wires.
Next, a filling resin, xe2x80x9cFILLxe2x80x9d, covers the chip and its wires in the space delimited by the resin band.
According to one essential characteristic of the invention, the resins used for the band and for the filling are both resins polymerizable by exposure to ultraviolet.
According to one particular feature of the invention, both resins contain mechanical reinforcing means and notably glass fibres.
A more particular object of the present invention is a method of manufacturing a portable electronic device with an integrated circuit, characterised in that it has the following steps:
deposition of a high-viscosity resin band, polymerizable by ultraviolet, around the integrated circuit chip and its connecting wires;
deposition of a low-viscosity filling resin, polymerizable by ultraviolet, in the space delimited by the resin band;
polymerization of the protective resins by exposure to ultraviolet.
According to one characteristic of the invention, at least the filling resin has mechanical reinforcing fibres.
According to one particular feature, the reinforcing fibres are glass fibres.
Advantageously, the percentages of glass fibres contained in the resins are between 5% and 20%.
According to another characteristic, the protective resins are cationic epoxy resins.
According to the preferential embodiment, the different steps of the method are carried out one after the other and continuously, and the polymerization step is carried out simultaneously on the two resins.
According to another characteristic, the resins also contain a small percentage of extractible fluoride ions, some of said ions being neutralized by addition of chemical compounds of magnesium.
According to one particular feature, the amounts of fluoride ions contained in the resins are between 20% and 40% of the usual concentrations, the latter being greater than or equal to 250 ppm.
According to another characteristic, the resins also contain elasticising agents comprising one or a mixture of a number of oligomeric alcohols.
According to one particular feature, the oligomeric alcohols are polyesters and/or polycarbonates and/or polyethers and/or polybutadienes and/or the copolymers thereof.
According to another characteristic, the resins also contain one or a mixture of a number of photoinitiators.
According to one particular feature, the photoinitiators are triarylsulphonium salts.
According to another characteristic, the resins also contain monomers and/or oligomers polymerizable cationically under ultraviolet.
According to one particular feature, the monomers and/or oligomers are cycloaliphatic epoxides.
According to one particular feature of the invention, the resin band has a viscosity greater than or equal to 150,000 cps.
According to another particular feature of the invention, the filling resin has a viscosity less than or equal to 6000 cps.
The present invention also relates to an electronic module having a chip transferred on to a dielectric support and connected to a communication interface, characterised in that it comprises a protection of the chip and of its connecting wires consisting of two distinct resins including at least one photoinitiator, a first resin constituting a band on the periphery of the protection and a second resin filling the space delimited by the resin band.
According to a variant embodiment, the resin band overlaps the chip and its connecting wires so as provide rigidity of the micromodule.
The method according to the invention is simple to implement and simplifies the prior methods.
In particular, the barrier deposition and milling steps are eliminated, and the polymerization time is considerably shortened by the use of resins cross-linked by ultraviolet. This allows significant productivity gains and unit manufacturing cost savings.
Deposition of the resin band is carried out in time masked in relation to deposition of the filling resin. The overall time for encapsulation of the chip and its wires is therefore equal to the time for depositing a drop of resin in the conventional xe2x80x9cglob topxe2x80x9d technique.
Furthermore, the method according to the invention uses photosensitive resins despite the prejudices generally associated with such resins.
In addition, the two resins are polymerized simultaneously in the continuity of the manufacturing method, following the depositions.
The method according to the present invention makes it possible to achieve manufacturing rates of 12,000 items per hour continuously.
Furthermore, the manufacturing method according to the invention has the advantage of having full control over the thickness of the chip protection.
In addition, the protection has good impervious qualities, since the two resins mix together slightly before being polymerized by simple exposure to ultraviolet in the continuity of the manufacturing line.
The nature of the resin band, in addition to its function of limiting the spreading of the protection, contributes towards the protection and rigidity of the micromodule.
The resins used in the method according to the invention make it possible to increase the quality and reliability of the electronic device obtained.